Necrotizing Otitis Externa
(Gallium Scan)

Necrotizing Otitis Externa
(Gallium Scan)

Description : Further investigations
It is critical that malignant otitis externa is diagnosed at an early stage so that appropriate treatment can be initiated before the osteomyelitis has spread beyond the possibility of treatment.

The first step towards the correct diagnosis is clinical suspicion (i.e. severe otitis externa in a diabetic or immunocompromised individual).

A gallium scan should then be done. Gallium 67 citrate will show the infected focus in the involved temporal bone by binding to the granulocytes.

Urinalysis and a blood sugar level should be carried out in any elderly patient with refractory otitis externa, especially if Pseudomonas has been cultured.

Treatment guidelines
In malignant otitis externa, simple aural toilet followed by the application of topical antibiotic drops are ineffective measures. These patients require urgent referral for a specialist opinion and admission to hospital.

The initial treatment includes scrupulous debridement of the ear, using the operating microscope, and an adequate course of both systemic and topical antibiotics which are effective against Pseudomonas.

The oral administration of a non steroidal anti-inflammatory preparation such as indomethacin may also be of substantial value. If an aminoglycoside antibiotic is used, serum levels and renal function should be carefully monitored to avoid possible ototoxicity and nephrotoxicity. Hyperbaric oxygen therapy may be of benefit as an adjunct to antibiotic treatment.

When medical treatment is unsuccessful, a wide surgical excision of the involved necrotic tissue is indicated. This may include removal of the pinna or even extirpation of a large part of the temporal bone.

Note the `hot' area of isotope uptake around the external auditory canal in this gallium scan of a patient with malignant otitis externa.

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